Two types of laminators which are suitable for producing plastic cards consisting of layers (laminate) by laminating, i.e. bonding together the layers, are known.
A first group works with oversized laminate layers which are placed between two heating plates and are laminated by a conventionally simultaneous action of heat and pressure. The non-defined boundaries of the finished laminate mean that in a second processing step after cooling said laminate then also has to be cut, namely punched, to the final dimensions of the card.
A second group for laminating or heat sealing suitable plastic cards comprises a hollow mold or cavity which holds the laminate to be laminated and straight away has the final dimensions of the card, and heating plates which are arranged above and below the cavity into which, as is known, cooling bodies are in turn assigned, and also pressure-exerting means which press the heating plates onto one another in such a manner that a laminate held between them is subjected to an appropriately dimensioned action of pressure and temperature for the short period of action.
A finished card is therefore immediately produced, the laminating always taking place until shortly before or at the softening point of the inserted material to a sufficient extent that an integral, finished card can be removed from the cavity.
Laminators of this type from the second group, as are revealed, for example, in the specifications DE 39 16 708 A1, DE 42 06 342 A1 or EU 0 669 214 A1, have a peripheral frame which bounds the receiving cavity and whose internal dimensions correspond to the final dimensions of the card thereby rendering the subsequent punching processing step superfluous. Laminators of this type which produce a finished, sized card and which are also referred to in the following as sizing laminators, generally also have a pressure-compensating body so as to ensure a uniform surface structure of the finished card and, in particular, also a uniform action of pressure during the laminating process.
However, the fact that the borders of the inserted laminate layers necessarily bear against the sized mold parts during the laminating process and therefore a loss of heat inevitably also occurs in these regions, so that although a uniform action of pressure can be spoken of, this type of heat sealing, i.e. laminating, does not succeed in also ensuring a uniform action of heat in all regions of the inserted material which is to be laminated, may be problematical in sizing laminators of this type.
The reason for this resides in the fact that only the heating plates on both sides have final dimensions, with the result that, when viewed purely physically, said heating plates necessarily already have a certain temperature gradient from the center to the boundary regions. However, this problem could be countered by an appropriately suitable distribution of the heating means—but what cannot be rectified in this manner, particularly if the shortness of the laminating time over which the action of pressure and temperature is maintained on the inserted laminate is included, is the fact that the boundary regions of the inserted material which is to be laminated which are pressed against the lateral, sized mold parts or come to bear against the latter lose heat in this region, with the result that the uniform distribution of the acting quantities of heat which is required over the entire surface of the laminate for a uniform laminating process cannot be ensured.
This means that the laminating possibly, or even with some degree of probability, does not take place completely, especially in the boundary region of the card, with the result that the layers which are to be bonded together may be broken open again from that point, for example for forgery purposes. This circumstance can also not be countered by simply heating more intensively overall, since this leads to excessive heating of the laminate in the central region, with the result that an undesirable fusing together of the material and possibly even of any information, data and the like which is present could occur. Such a measure would also not be conducive for inserted electronic parts.